feat(web): 添加剪贴板复制兼容 HTTP 环境

- 新增 useClipboard composable，支持 execCommand 备用方案
- 修复 HTTP 环境下复制按钮无响应问题

web/src/composables/useClipboard.ts

@@ -0,0 +1,65 @@
+import { ref } from 'vue'
+
+export function useClipboard() {
+  const copied = ref(false)
+
+  // 检测是否支持原生 Clipboard API (需要安全上下文 + API 存在)
+  function canUseClipboardApi(): boolean {
+    return !!(
+      typeof navigator !== 'undefined' &&
+      navigator.clipboard &&
+      typeof navigator.clipboard.writeText === 'function' &&
+      window.isSecureContext
+    )
+  }
+
+  // Fallback: 使用 execCommand (兼容 HTTP 环境)
+  function fallbackCopy(text: string): boolean {
+    const textarea = document.createElement('textarea')
+    textarea.value = text
+    textarea.style.cssText = 'position:fixed;top:0;left:0;opacity:0;pointer-events:none'
+    document.body.appendChild(textarea)
+    textarea.focus()
+    textarea.select()
+
+    let success = false
+    try {
+      success = document.execCommand('copy')
+    } catch {
+      success = false
+    }
+
+    document.body.removeChild(textarea)
+    return success
+  }
+
+  async function copy(text: string): Promise<boolean> {
+    if (!text) return false
+
+    try {
+      if (canUseClipboardApi()) {
+        await navigator.clipboard.writeText(text)
+      } else {
+        if (!fallbackCopy(text)) {
+          return false
+        }
+      }
+
+      copied.value = true
+      setTimeout(() => (copied.value = false), 2000)
+      return true
+    } catch (e) {
+      // Clipboard API 失败时尝试 fallback
+      console.warn('Clipboard API failed, trying fallback:', e)
+      if (fallbackCopy(text)) {
+        copied.value = true
+        setTimeout(() => (copied.value = false), 2000)
+        return true
+      }
+      console.error('Copy failed:', e)
+      return false
+    }
+  }
+
+  return { copy, copied }
+}